Method of forming studs



Oct. 29, 1968 w. M. JONES 3,407,641

METHOD OF FORMING STUDS Filed June 23. 1966 3 Sheets-Sheet l INVENTOR. WILLIAM M. JONES BY 4%, mild/14M ATTORNEYS Oct. 29, 1968 w. M. JONES METHOD OF FORMING STUDS 5 Sheets-Sheet 2 Filed June 23. 1966 G W T H P 0 l 9 I H E S M a s M R G L am w Wm m M mm i 0 E C M D 0% R H GP G m m P D. 7 G F.

l2 RELOCATE IIANNEAL STATIONS INVENTOR. WILLIAM M. JONES FIG.8

ATTORNEYS Oct. 29, 1968 w. M. JONES METHOD OF FORMING STUDS 3 Sheets-Sheet 3 Filed June 23, 1966 FIG.9

lvllllall H ANNEAL IZRELOCATE INVENTOR. M. JONES ATTORNEYS WILLIAM F|G.|l BY 4%, SW 61 Mal/10M United States Patent 3,407,641 METHOD OF FQRMING STUDS William M. Jones, Big Flats, N.Y., assignor to The Youngstown Steel Door Company, Cleveland, Ohio, a corporation of Ohio Filed June 23, 1966, Ser. No. 560,002 Claims. (Cl. 72--349) This invention relates to a method of forming apertures mask supporting studs for television pictures tubes. More specifically, this invention relates to a method of stamping metal studs which will be bonded to glass television tubes to accurately locate and support thermally compensated formed shadow masks.

In color television tubes a mask having apertures therein is mounted on the inside of a sealed cathode ray tube. The aperture mask is suspended within the tube in close proximity to a phosphor dot screen by means of metallic studs which are partially embedded in the glass wall of the tube. Because of the delicate nature of the glass and the precision register reqiured of the mask, screen and the electron gun, it is extremely important that the same relative positions are maintained at all times.

The apertures in the mask focus the electron beams to minimize color contamination by preventing each beam from hitting the Wrong phosphor dot or overlapping several dots at the same time. The studs act positively to hold the critical relative positions, thereby minimizing discoloration and fuzziness caused by temperature variations, impacts, or vibration.

In order to maintain the precise register between the mask and the screen, the studs which suspend the mask should have very nearly the same coefficient of thermal expansion as the glass of the color tube over the entire temperature range at which the color picture tube operates.

One reason for the same coeflicient of thermal expan sion for the glass tube and studs is that breakage of the glass could occur if one of the materials expanded faster than the other. Another and more important reason results from the method of assembling the tube.

The color television tube usually comes in two portions: a phosphor dot screen supporting face plate and an electron gun supporting funnel shaped body. These sections are sealed together to form the complete tube envelope and a vacuum created therein. However, before assembly and joining of the two sections, an aperture mask is mounted on the partially embedded studs near the screen in perfect register with the phosphor dots. The tube face plate portion in which the studs is embedded is not assembled to the funnel shaped body until after this operation is complete. The studs are embedded in the glass at points which have been softened by localized heating. Because of the complexities of manipulation during this procedure it is necessary for the inside of the face plate portion, in order to be accessible, to be exposed to the atmosphere. Consequently, some air is trapped in the central cavity of the studs in this step. A danger exists in contaminating the inside of the tube if this air is released. The air may be released by damage to the glassmetal seals or separation of the studs from the glass due to a difference in the thermal coefiicients of expansion of the metal and glass.

Certain types of stainless steel, which have the desired coeflicient of thermal expansion are known to the art. Because of their hardness and lack of malleability, however, these metals are not readily die formed into desired shapes, particularly if a drawing operation is required. Accordingly, it previously was thought that because of this lack of formability and the specific shape of the studs, that it was necessary to machine the studs. For production purposes they have been made from bar stock on screw machines. No metals which are easily die formed and 3,407,641 Patented (Dot. 29, 1968 drawn have the correct coetficient of thermal expansion.

The novel method of producing the studs by die forming, according to the principles of this invention, has significantly lowered the cost of studs for television tubes. Economy in the manufacturing operations involved in stud making are a primary consideration since the amount of material involved for each stud is small.

A description of a stud will indicate the difficulty in die forming it. A typical color television tube stud comprises a crown having a generally fiat uppermost portion and tapered sides. The taper of the sides on the inside is approximately 12 from the vertical and graduates into a shoulder which is approximately 3 below the horizontal. Below the shoudler is a skirt. The side of the skirt tapers toward its center axis and the inner surface of the skirt tapers away from its axis thus creating a. wedge-like crosssection.

The inside of the crown forms a cavity above the main cavity of the skirt.

The present invention proposes a method of die forming and drawing stainless steel to produce the desired form. It has been found that the use of successive dies for forming the crown and drawing and setting the skirt will produce the required angles of the sides and crown from stainless steel material.

The present method of forming studs from a blank strip of stainless steel metal generally comprises shearing sections of metal from the strip at spaced intervals, shaping crowns by successive die forming operations, and coining them to obtain the desired crown shape with metal available for subsequent drawing. Annealing of the stainless steel to acquire the desired hardness and ductility is then performed, subsequent to which the metal is drawn about the crown to form a skirt and set by means of opposing dies. The skirt is then sheared off at the bottom and the stud is reset in dies to accurately form the angular relationship required.

FIG. 1 indicates a stud 10 which is formed by the process of this invention. It has a crown 11 and a skirt 12.

The crown 11 has a flattened top portion 13 and an outwardly tapering wall or side 14. The tapered wall 14 is integral with a tapered shoulder 16 which acts as the connector between the wall 14 of the crown 11 and the skirt 12.

FIG. 2 is a cross-sectional view taken along section 2-2 of FIG. 1. As seen in FIG. 2 the outside surface of the skirt 12 is slightly inwardly tapered and forms an angle of approximately 2 with the vertical. The inside surface 18 of the skirt 12 is tapered outwardly approximately 18. The converging tapers of the skirt result in a wedge-like cross-section terminating in a bottom surface 19.

Immediately above the inside surface 18 of the skirt 12 is a hollow recess 20 which is an extension of the larger opening defined by the surface 18 and which defines a cavity on the inside of the crown 11.

The outer surface 14 of the crown 11 has an outwardly directed taper with the vertical of approximately 12. The shoulder 16 which is immediately adjacent the crown 11 has an angle of approximately 3 below the horizontal. While the 'above angles are not critical, the shape of the stud is very important for reasons which will be more fully explained hereinafter.

FIG. 3 illustrates the use of the studs 10 for suspending a color television aperture mask 22 in a color television picture tube 23. As therein illustrated, the studs 10 form an integral metal-to-glass contact with the picture tube 23. The crown 11 of the studs 10 engage brackets 24 to accurately hold the mask 22 in place.

FIG. 4 is an enlarged view of the metal-to-glass relationship shown in FIG. 3. This view clearly shows that the skirt 12 forms an integral bond with the color picture tube 23. The bond is formed by locally heating the glass until it is softened and then pressing the bottom 19 of the skirt 12 into the glass. The wedge-like cross section of the skirt 12, as well as the shoulder 16, greatly facilitates the accurate insertion of the stud 10 into the glass and facilitates the integrity of the bond. The shoulder 16 acts as a surface on which an axial force may readily be applied to the stud 10 to force it into tlle softened glass tube 23.

The crown 11 is tapered so that it may fit into and suspend the bracket 24 along the side of the crown 11 approximately halfway down from its top portion 13. The narrow top of the crown has a diameter which may be easily inserted in the opening 26 of the bracket 24. As the crown 11 proceeds through the opening 26, its wider section eventually engages the bracket 24 at three oints.

FIGS. and 11 illustrate the relation of the crown l1 and the bracket 24 with the aperture mask 22 suspended and properly located. The opening 26 has a triangular shape to cooperate with the surface 14 to insure accurate register of the mask 22 with the phosphor dot screen 25. The crown 11 is pushed into the opening 26 of the bracket 24 in order to maintain a relatively rigid relationship. The triangular opening 26 in the bracket 24 provides an accurate locating and centering function because the circular cross section of the crown is naturally centered by the triangular shape of the opening 26 as the crown is inserted therein.

FIG. 6 illustrates a cross-sectional view of the stud in its bonded position with the glass tube 23. It can be seen from this view that the skirt 12 is in intimate contact over its inner and outer surfaces with the glass of the tube 23. This prevents expansion and contraction of the skirt 12 at a different rate than the glass of tube 23, to avoid breaking or cracking of the tube 23 or breaking of the metal-glass seal in a manner which would release the air trapped in the central cavity. As discussed earlier, the air is trapped in the cavity during assembly and must be kept from contaminating the inside of the tube.

FIG. 7 is a block diagram showing the steps of the method of this invention. The method defined therein is illustrated in FIG. 8 and its cross sectional view FIG. 9. The blank material in this case are preferably strips of stainless steel metal having a width and thickness suflicient to provide enough metal for the die forming process to form the stud 10. One of these stainless steel materials that may be used in the present invention is that shown as Sylvania No. 4 alloy which has a chemical analysis of:

Nickel percent bogie 42.0 Chromium do 5.6 Manganese percent max 0.25 Silicon do 0.30 Aluminum do 0.20 Carbon do 0.07 Phosphorous do 0.25 Sulphur do 0.25 Iron balance This material has a coefficient of expansion of 9.6 times l0- to 10.2 times 10- in./in./ C. Another metal which has similar properties and is possible to use in the present invention is known as Sealmet HC4 which has a generally similar composition. Both of the above metals have a coefficient of thermal expansion very similar to that of the glass used in these tubes, that is, approximately 8 to 9 10 in./in. C.

The first step of the process is to shear out of the plane of the metal, at regular intervals, hourglass shaped areas of metal. The area shown at station 1 in FIGS. 8 and 9 results.

Steps 2 through 9 indicate a progressive shaping of the blank strip of metal. Progressive shaping is necessary because of the hardness and lack of ductility of the stainless steel used for the studs. if the stud was attempted to be die formed in one step, the metal would then break and fold. The subsequent procedure comprises progressive die forming of the dome-shaped abutment shown in section 2. In areas 3 and 4 of FIGS. 8 and 9, the diameter of the dome-shaped abutment or protrusion is reduced in length and simultaneously raised in height. In sections 5 and 6 the protrusion is next flattened on its top portion and again reduced in diameter. This procedure is continued in sections 7 through 9 where the exact dimensions and angles are obtained by several steps of pressing the top portion flat while reducing the diameter of the protrusion. The protrusion acquires its shape as crown 10 in section 10. This gradual progressive shaping including the initial step of forming an oversized abutment, enables a crown 10 to be formed while maintaining the thickness of the metal.

In area 10 the metal undergoes a process known as coining. Coining is generally defined as a step of press: ing cold metal so that only restricted fiow is permitted. That is, flow is restricted in a direction perpendicular to the direction of the forces applied. The crown 10 is coined in order to obtain the exact thickness, angles, and dimen sions that are necessary. The area around the crown 10 is coined in order to slightly taper it and thus prepare the shape for drawing. That is, the metal near the crown is made thicker so that the drawing step may use the excess in forming the thick shoulder 16 and tapered skirt 12.

After the crowns have been coined, the blanks and the crowns which have been formed therein are annealed. A block between areas 10 and 13 illustrates that the entire strips must be physically placed in a furnace and annealed and then relocated on the production line. When the strips are placed in the furnace, they will have the completed coined crowns formed therein and will not have the crowns in various stages of formation as shown in FIGS. 8 and 9. A temperature of 1850 F. for ten minutes provides the desirable tensile strengths and coeflicients of elasticity for the metals stated to permit the metal to be drawn. Subsequently, the annealed crowns are accurately relocated in the dies for the following steps.

As illustrated in areas 13 through 15, the metal is drawn upward toward the crown from the plane of the blank. This step forms a tapered skirt under the crown which is connected to the crown by means of a shoulder.

The formed skirt is then pressed between dies or set to insure that it is properly formed and positioned for the shearing step. The positioning of the stud is of utmost importance since it determines exactly where the skirt will be sheared from the strip. Any mislocation could ruin the studs. Subsequently, the stud is pinched off or sheared about its lowermost portion of the skirt. It is then reset or reformed in order to insure the precise angular relationships of the inner and outer walls of the crown, shoulder and skirt which may have been distorted by the shearing process. The resetting step is illustrated in FIG. 10.

For ease of description, the principles of the invention have been set forth in connection with but a single illustrated embodiment. It is not my intention that the illustrated embodiment nor the terminology employed in describing it be limiting inasmuch as variations in these may be made without departing from the spirit of the invention. Rather I desire to be restricted only by the scope of the appended claims.

I claim:

1. A method of making television picture tube studs having a crown, a shoulder and a skirt portion from a blank of steel comprising:

shearing areas of the steel atspaced intervals,

die forming crowns between said sheared portions,

coining said areas to form thickness differences among the metal of the crowns, the metal to become the shoulders and the metal to become the skirts,

annealing said steel to increase its ductility,

drawing the metal surrounding the crowns to form shoulders and skirts,

setting the desired dimensions of the studs by means of dies,

pinching off the bottom of said skirts from said areas,

and

resetting said studs in dies to accurately form a definite final dimension of the studs.

2. A method of making television picture tube studs having a crown, a shoulder and a skirt portion from a blank of steel comprising:

die forming crowns at intervals along said blank,

coining said crowns and the metal around said crowns to form a specified thickness,

annealing said steel to increase its ductility,

drawing the metal around the crowns to form shoulders and skirts, and

severing the bottom of said skirts from said blanks.

3. The method of claim 2 wherein areas of metal are sheared from said blank at spaced intervals before said crowns are die formed.

4. The method of claim 3 wherein said sheared portions have an hourglass shape.

5. The method of claim 2 wherein said step of die forming the crowns comprises:

pressing portions of the blank out of their original plane so as to form dome-shaped protrusions, reducing the diameter of said dome-shaped protrusincreasing the height and simultaneously further reducing the diameter of said dome-shaped protrusions, and

further reducing the diameter of said dome-shaped protrusions and flattening the topmost portion of the crowns.

6. The method of claim 2 wherein said blank is stainless steel and said step of annealing is done at approximately 1850 F. for approximately ten minutes.

7. The method of claim 2 wherein the desired dimensions of the studs are set by means of dies after the metal has been drawn to form shoulders and skirts and before the skirt is severed from the blank.

8. The method of claim 7 wherein said studs are reset in dies to accurately form definite final dimensions of the studs after they have been severed from said blanks.

9. The method of claim 8 wherein said step of resetting is accomplished by pressing said studs between an inner die having a surface which fits inside said studs and said crowns and an outer die.

10. A method of making television picture tube studs having a crown, a shoulder and a skirt portion from a blank of stainless steel comprising:

shearing hourglass shaped portions from said blank at intervals along its length,

forming crowns between said intervals by the steps comprising: pressing portions of the blank out of their original plane so as to form dome-shaped protrusions, reducing the diameter of said dome-shaped protrusions, increasing the height and simultaneously further reducing the diameter of said dome-shaped protrusions, and further reducing the diameter of said dome-shaped protrusions and flattening the topmost portion of the crowns,

coining said crowns and the metal around said crowns to form a specified thickness (of the metal of the crowns and its surrounding areas),

annealing said stainless steel at 1850 F. for approximately ten minutes to increase its ductility,

drawing the metal around said crowns to form shoulders and skirts,

setting the desired dimensions of the studs by means of dies,

pinching off the bottom of said skirts from said blanks,

and

resetting said studs in dies to accurately form definite final dimensions of the studs.

References Cited UNITED STATES PATENTS 1,752,982 4/1930 Herold 10-86 2,434,905 1/1948 Burr et a1. 72--349 3,289,523 12/1966 Kramer -35 RICHARD J. HERBST, Primary Examiner.

Dedication 3,407,641.Wz'll2'am M. Jones, Big Flats, N.Y. METHOD OF FORMING STUDS. Patent dated Oct. 29, 1968. Dedication filed Sept. 28, 1970, by the assignee, Youngstown Steel Door Company.

Hereby dedicates the entire term of said patent to the Public.

[Oflioial Gazette J anuary 1.9, 1971] 

1. A METHOD OF MAKING TELEVISION PICTURE TUBE STUDS HAVING A CROWN, A SHOULDER AND A SKIRT PORTION FROM A BLANK OF SHEET COMPRISING: SHEARING AREAS OF THE STEEL AT SPACED INTERVALS, DIE FORMING CROWNS BETWEEN SAID SHEARED PORTIONS, COINING SAID AREAS TO FORM THICKNESS DIFFERENCES AMONG THE METAL OF THE CROWNS, THE METAL TO BECOME THE SHOULDERS AND THE METAL TO BECOME THE SKIRTS, ANNEALING SAID STEEL TO INCREASE ITS DUCTILITY, DRAWING THE METAL SURROUNDING THE CROWN TO FORM SHOULDERS AND SKIRTS, SETTING THE DESIRED DIMENSIONS OF THE STUDS BY MEANS OF DIES, PINCHING OFF THE BOTTOM OF SAID SKIRTS FROM SAID AREAS, AND RESETTING SAID STUDS IN DIES TO ACCURATELY FORM A DEFINITE FINAL DIMENSION OF THE STUDS. 